Alzheimer's Disease

I

Introduction

Alzheimer's Disease, commonest form of dementia. It causes progressive irreversible damage to the brain and usually leads to death within a few years of its onset. Its cardinal symptoms are loss of memory followed by a more general impairment in mental functioning and disturbance in behaviour. It is increasingly common with age, so that about a third of those over 90 years old will be affected. With the growing number of elderly, it has become one of the most serious social and health problems of developed countries.

II

History

Both Virgil (Eclogue IX) and Cicero (Cato: On Old Age) wrote about the decline of memory in old age. In the 19th century severe memory problems in the elderly were called senile dementia, and were thought to be caused by reduced blood circulation due to narrowing of the brain’s arteries. In 1906 a pathologist, Alois Alzheimer from Munich, Germany, described a severe case of pre-senile dementia in a woman of only 51 years. She had memory problems, was disoriented, and had delusions. On autopsy, Alzheimer discovered that the blood vessels did not show the typical changes of senile dementia. Instead, he found that the brain contained large amounts of two distinct structures: the so-called amyloid plaques (deposited outside the nerve cells) and neurofibrillary tangles (deposited within nerve cells). This characteristic disease soon became called Alzheimer’s disease, and for many years it was thought to be distinct from senile dementia because it only occurred in younger people. However, since the 1960s it has been recognized that the common form of senile dementia in old age is in fact the same that Alzheimer described, and that the dementia caused by changes in the arteries is less common.

III

Occurrence

Alzheimer’s disease is rare before the age of 60. In those aged 65-70 years, about 1-2 per cent have it, and the proportion of persons with Alzheimer’s disease approximately doubles for each successive 5 years of age, such that by the age of 90 about 30 per cent have Alzheimer’s disease. The proportion of elderly people in the populations of developed countries has risen dramatically as life expectancy has increased and, as a result, the numbers with Alzheimer’s disease are very large and still growing. In the UK there were about 600,000 people affected by the condition in 2000, but the number in 2050 is projected to be 1.1 million. For the United States the figures were about 2.5 million in 2000, projected to rise to 8 million in 2050. The number of new cases that arise each year in the US is predicted to rise from about 400,000 in 2000 to 1 million in 2050. In the future, similar effects will be seen in developing countries as life expectancy there increases.

IV

Symptoms

The symptoms of Alzheimer’s disease vary between individuals but there are certain common features. The disease is usually first noticed by problems with short-term (recent) memory that may initially be put down to the changes of normal ageing. However, if the forgetfulness is persistent (for example, if the person repeatedly asks the same question within a few hours), and especially if it involves forgetting not so much where things are but what they are used for, then it is likely to be due to a disease process. Other changes in this early phase may include disorientation, such as getting lost in familiar surroundings, missing appointments, or doing things at inappropriate times. Relatives may be accused of hiding or stealing things, and signs of irritability may cause distress to others. Difficulty in language, such as finding words, may occur. People in employment begin to have problems in dealing with common situations. The afflicted person may be aware of their problems and frequently they become depressed.

The next stage of the disease is characterized by changes in the activities of everyday life that immediately become obvious to those around the person. Difficulty in dressing, in laying the table for a meal, shopping, and sometimes in personal care can occur. The sufferer may be found wandering away from home. Speech and behaviour are affected, which leads relatives to think that there has been a change in personality. Sometimes, psychotic symptoms occur, such as delusions and hallucinations. This is a particularly trying time for friends and relatives. It lasts about three or four years.

The final stage is one of complete dependence, when the person often stays put for many hours at a time and needs constant care and support. Memory loss is often total with the upsetting result that the spouse or child is no longer recognized. Physical changes may become apparent. Eventually, the sufferer cannot cope with common infections and may die from pneumonia or a urinary tract infection. This phase lasts about two years.

The time-course of Alzheimer’s disease varies, but from first symptoms to death is usually about seven to eight years. Younger sufferers (those below 60) often show a more rapid progression, while some older patients may survive for 10 or 15 years.